1. Field of the Invention
The present invention relates to a mechanism for preventing the malfunction of a variable output device built in various electronic apparatuses.
2. Description of the Related Art
Conventional electric apparatuses are available which comprise a variable output device such as a variable resistor and an operating unit therefor. The operating unit is a knob for manipulating and therefore adjusting the variable output device from outside the apparatus.
FIG. 10 shows a mounting structure of a conventional operating unit 5. A variable output device 2 is connected by solder to a circuit board 1. The variable output device 2 has an operating shaft. The operating unit 5 is fitted on the operating shaft of the variable output device 2 to rotate integrally with the operating shaft. A part of the operating unit 5 is projected out of the electronic apparatus by way of a hole formed in an exterior case 7 of the electronic apparatus. The user adjusts the output of the variable output device 2 by rotating the operating unit 5 projected out of the apparatus. Various parameters of the electric apparatus are adjusted based on the output (amount of electricity, etc.) from the variable output device 2. A single-unit video camera recorder, for example, uses this type of a variable output device for adjusting the voice level to be recorded.
The conventional mounting structure of the variable output device is not provided with a lock mechanism for preventing malfunction. Under an incidental external force or with an inadvertent operation of the operating unit 5 by the user, the operating unit 5 is undesirably rotated against the will of the user, with the inconvenient result that the parameters of the electric apparatus are unduly changed.
In a single-unit video camera recorder, for example, a malfunction of the operating unit of a variable output device for adjusting the voice level may change the voice level against the intention of the user during the recording operation.